Ganciclovir administration rescues NOD/scid mice from severe GvHD induced by baCD3/CD28-TK⁺ human lymphocytes. At the time of severe GvHD, NOD/scid mice were treated with GCV or with saline. (A) Individual recipients of PBL (left graphs) or baCD3/CD28-TK⁺ lymphocytes (right graphs) were implanted subcutaneously either with a saline-filled or a GCV-releasing osmotic pump. At days 0, 7, and 14 from the implantation of the pumps mice were assessed for human chimerism by flow cytometry (▪) and scored for GvHD by a clinical index (□, top histograms). Mice were also followed for weight loss and mortality over time (bottom curves). Open arrows indicate saline; dashed arrows, GCV administration. The broken horizontal line is set at 95%. Results from one representative mouse per condition are shown. (B) Available mice infused with PBLs (left graphs) or with baCD3/CD28-TK⁺ lymphocytes (right graphs) and either treated with saline or with GCV were analyzed by histopathology and scored. GCV-rescued mice were humanely killed at the end of the study, 120 days after the infusion of baCD3/CD28-TK⁺ cells. Each symbol represents the spleen, gut, or liver score of individual animals. (C) Histologic sections from the spleen, liver, and gut of representative animals infused with baCD3/CD28-TK⁺ lymphocytes and treated either with saline (top row) or with GCV (bottom row) are reported.